A large variety of additives for improving various properties in hydrocarbon oil compositions are well known, and in fact a large number of these compositions are being used on a commercial level. The various additives are used for a variety of purposes, many of which relate to improving the low temperature (i.e., less than about 30.degree. F.) flow properties of various types of hydrocarbon oils, including both lubricating oil fractions and other oil fractions including heating oils, diesel oils, middle distillates, and the like. In particular, these flow improvers generally modify the wax crystals in both lubricating oils and other hydrocarbon fractions and crudes so as to impart low temperature handling, pumpability, and/or vehicle operability thereto. These parameters are generally measured by a variety of tests, including pour point, cloud point, mini-rotary viscometry (MRV) and others. Other such additives are used primarily for imparting other properties to these hydrocarbon fractions, including lubricating oil fractions, such as anti-oxidant properties and the like.
Cloud point (ASTM D 2500) is the temperature at which wax crystals first appear as a haze in a hydrocarbon oil upon cooling. Such wax crystals typically have the highest molecular weight of the waxes in the hydrocarbon oil and therefore the lowest solubility. The cloud point of a hydrocarbon oil reflects the temperature at which problems in filtering the oil are encountered. However, the cloud point of a lubricating oil (as opposed to a fuel oil) is of less significance than is its pour point because the filters typically encountered by a lubricating oil (e.g., combustion engine oil filters) have a relatively large pore size, and filter plugging is therefore less of a problem in these environments.
Pour point is the lowest temperature at which a hydrocarbon oil will pour or flow when chilled, without disturbance, under specified conditions. Pour point problems arise through the formation of solid or semi-solid waxy particles in a hydrocarbon oil composition under chilled conditions. Thus, as the temperature of the oil is decreased, the distribution of such oil by pumping or siphoning is rendered difficult or impossible when the temperature of this oil is around or below the pour point of the oil. Consequently, when the flow of oil cannot be maintained, equipment can fail to operate.
It has therefore been necessary to develop various additives for the purpose of influencing the cold temperature flow properties of hydrocarbon oils.
The general term "lubricating oil flow improver" (LOFI) covers all those additives which modify the size, number, and growth of wax crystals in lube oils in such a way as to impart improved low temperature handling, pumpability, and/or vehicle operability as measured by such tests as pour point, cloud point, and mini rotary viscometry (MRV). The majority of lubricating oil flow improvers are polymers or contain polymers. These polymers are generally of two types, either backbone or sidechain.
The backbone variety, such as the ethylene-vinyl acetates (EVA), have various lengths of methylene segments randomly distributed in the backbone of the polymer, which associate or cocrystallize with the wax crystals inhibiting further crystal growth due to branches and non-crystallizable segments in the polymer.
The sidechain-type polymers, which are the predominant variety used as LOFI's, have methylene segments as the side chains, preferably as straight side chains. These polymers work similarly to the backbone type except the side chains have been found more effective in treating isoparaffins as well as n-paraffins found in lube oils. More specifically, LOFI's are typically derived from unsaturated carboxylic acids or anhydrides which are esterified to provide pendent ester groups derived from a mixture of alcohols. Most current commercial additives of this type thus require the use of relatively expensive alcohols for their production. Representative examples of this type of side chain LOFI include dialkyl fumarate/vinyl acetate copolymers and esterified styrene/maleic anhydride copolymers.
It would be extremely advantageous if additives could be developed which rely on less expensive olefins rather than alcohols in the synthesis of low temperature flow improves without sacrificing the properties of conventional alcohol-based LOFI's. Several commercially unsuccessful attempts have been made in the past using alkylated phenol formaldehyde condensates.
One additive composition which has been disclosed as a pour depressant for fuels and crude oils is set forth in British Patent No. 1,173,975. The additive disclosed in this patent is a phenol-aldehyde (preferably formaldehyde) polymer in which the phenol has an R - or RCO - substituent in which R is hydrocarbyl or substituted hydrocarbyl. R is further said to contain from 18 to 30 carbon atoms, and is preferably a straight chain alkyl group. The specific examples in this patent which use olefins to provide these R groups include various internal olefins, and there is no specific disclosure regarding the advantages of using terminal olefins therein. Another patent, British Patent No. 1,167,427, discloses the use of esters of such phenol-aldehyde polymers for pour point reduction of fuel oils. In both of these British patents, the oils to be treated are said to have a maximum viscosity of about 1500 cSt at 100.degree. F., neither recognizes the significance of utilizing specific alpha-olefins and mixtures thereof to produce these condensation products or the advantages of imparting essential linearity to the olefin-derived side chains.
Another additive composition which has been disclosed for use as a pour point depressant, so as to modify the surface of the wax contained within lubricating and fuel oil compositions by absorption or co-crystalization so as to reduce the fluid occlusion by these crystals, is a phenolic compound disclosed in U.S. Pat. No. 3,336,226. The compound shown in this patent is an alkyl phenol trimer having methylenic bridges which is mono-substituted by alkyl groups of between 14 and 25 carbon atoms. This patent specifically discloses trimeric compositions having number average molecular weights far lower than 3,000, in fact, lower than 1,500, and furthermore broadly discloses the use of olefins for alkylation of the phenol compositions prior to condensation with formaldehyde. The olefins disclosed in this patent are either terminal or internal olefins, and a trimer is prepared by conducting the condensation reaction in the presence of a metal hydroxide. Moreover, alkylation process conditions are not controlled to minimize rearrangement of even the terminal olefins.
Another lubricating oil composition is disclosed in U.S. Pat. No. 3,248,361. In this case cylinder lubricants are modified in order to reduce combustion chamber deposits by using an additive product of an olefin oxide with either a sulfur modified condensation product of a substituted monohydric phenol that includes a hydrocarbon substituent containing from 4 to 18 carbon atoms and an aliphatic aldehyde, or a partial salt of that sulfur-modified condensation product and an alkali metal, ammonia, or a Group II metal. This patent does not disclose a condensation product of an alkylated phenol and an aldehyde. U.S. Pat. No. 3,951,830 discloses lubricant additives particularly used as oxidation inhibitors comprising sulfur and methylene bridged polyphenol compositions. These are prepared by reacting phenol with formaldehyde followed by sulfurization or by sulfurizing phenols prior to reaction with formaldehyde. This patent also discloses phenols which are substituted with aliphatic or cycloaliphatic radicals of a wide range and variety, and it also discloses the use of poly-substituted materials, such as dialkyl and trialkyl phenols therein. All of the examples in this patent employ tetrapropene, polyisobutene, and other such substituted phenol compositions therein, and not essentially linear alkylated phenols of a specified length.
U.S. Pat. No. 4,446,039 discloses yet another additive for fuels and lubricants which, in this case, is prepared by reacting aromatic compounds, such as phenol or substituted phenol including alkyl groups of at least 50 carbon atoms, with an aldehyde, such as formaldehyde, and a non-amino hydrogen, active hydrogen compound, such as phenol, optionally along with an aliphatic alkylating agent of at least 30 carbon atoms. This patent also discloses that sulfurized additive compositions thereof can also be used as lubricant additives and fuel oil additives. It does not disclose the use of alpha-olefins of less than 50 carbon atoms for the alkylation of phenol.
Another additive for improving the various cold flow characteristics of hydrocarbon fuel compositions is disclosed in U.S. Pat. No. 4,564,460. In this patent the additives are broadly disclosed as including either an oil soluble ethylene backbone polymer or various hydrocarbyl-substituted phenols as a first component and various reaction products of hydrocarbyl-substituted carboxylic acylating agents and amines and/or alcohols. The hydrocarbyl-substituted phenol constituents of this overall additive are also broadly described, and they can include repeating aromatic moieties, such as those shown in column 14 thereof, in which the R* groups include hydrocarbyl groups of from 8 to 30 carbon atoms. These, in turn, can be provided by internal olefins or alpha-olefins, and can be either straight or branched. Notwithstanding the extremely broad disclosure of this patent, not a single working example is provided therein which makes or tests any hydrocarbyl substituted phenol or aldehyde condensation product thereof.
British Pat. No. 2,062,672 discloses another such additive, in this case including a sulfurized alkyl phenol and a carboxylic dispersant. The alkyl phenols disclosed in this patent can include alkyl radicals of up to 1000 carbon atoms, but the disclosure also mentions the use of methylene-bridged alkyl phenols prepared by the reaction of the alkyl phenol and formaldehyde.
Finally, Canadian Patent No. 1,192,539 discloses yet another alkyl-phenol-containing lubricant additive. In this case the lubricant is designed for two-cycle engines and the phenolic compound includes a hydrocarbyl group of an average of at least ten aliphatic carbon atoms. Furthermore, the disclosure states that the aromatic ring can be a linked polynuclear aromatic moiety, which can also include other substituents. Once again in this case the disclosure is very broad, and includes innumerable variations on the alkyl phenol component.
Irrespective of all of the above, and the large number of additive compositions which have previously been proposed and utilized for altering the various flow properties of hydrocarbon oils and lubricating oil compositions, the search has continued for additional flow improving compositions which can not only significantly improve the flow characteristics of these various hydrocarbon compositions, but which also can be easily produced on an economical basis.
Commonly assigned U.S. patent application Ser. No. 07/107457, filed on Oct. 8, 1987 by the inventors herein is directed to sulfur bridged alkyl phenol condensates, derived from the alkylated phenols described herein and used for the purposes described herein.